1. Field of the Invention
The present invention relates in general to an audio processing circuit and pertains, more particularly, to a circuit that is adapted for automatic operation in a partial distortion mode of operation. Even more particularly, the invention relates to an audio processing circuit that enables transition from distortion operation to a bright clean audio sound without losing output volume or treble if the instrument volume is turned down.
The principles of the present invention are described herein primarily in connection with the amplification and processing of audio signals from a guitar-type instrument. However, it is understood that the principles of the invention may also be applied in connection with the detection of audio signals from other types of musical instruments.
2. Background Discussion
An audio processing circuit of the general type described herein is disclosed in U.S. Pat. No. 4,584,700. Such a device includes circuitry for providing guitar sounds from very cleans sounds to very distorted sounds. In this connection the device includes a mode selector which basically divides the spectrum of guitar sounds into multiple catagories. These catagories include a distortion mode, a partial distortion mode referred to herein as an "edge" mode, and one or more clean sound modes.
When playing in the partial distortion or "edge" mode of operation the musician may want to turn the volume down to provide a cleaner and less distorted signal. However, with existing systems this creates a number of problems. First, there is a loss of volume that is undesired. Second, as one turns down the volume there is a tendency to lose high end frequencies. This occurs due to the interaction of the volume potentiometer with the pickup device.
Accordingly, it is an object of the present invention to provide an improved audio processing circuit and one which in particular provides, in a partial distortion mode of operation, means for providing a compensating boost in output volume as the volume potentiometer is turned down.
Another object of the present invention is to provide an improved audio processing circuit in which, in said partial distortion mode of operation, the high end frequencies are boosted at low volume settings.
A further object of the present invention is to provide an improved audio processing circuit that allows one to change from at least a partially distorted sound to a clean sound simply by adjusting the instrument volume control. This operation is unlike typical guitar/amplifier responses in which volume and treble usually disappear as the volume knob is turned down.